3,492 research outputs found
A new bridge between leptonic CP violation and leptogenesis
Flavor effects due to lepton interactions in the early Universe may have
played an important role in the generation of the cosmological baryon asymmetry
through leptogenesis. If the only source of high-energy CP violation comes from
the left-handed leptonic sector, then it is possible to establish a bridge
between flavored leptogenesis and low-energy leptonic CP violation. We explore
this connection taking into account our present knowledge about low-energy
neutrino parameters and the matter-antimatter asymmetry observed in the
Universe. In this framework, we find that leptogenesis favors a hierarchical
light neutrino mass spectrum, while for quasi-degenerate and inverted
hierarchical neutrino masses there is a very narrow allowed window. The
absolute neutrino mass scale turns out to be m < 0.1 eV.Comment: 10 pages, 3 figure
Texture Zeros and Weak Basis Transformations
We investigate the physical meaning of some of the "texture zeros" which
appear in most of the Ansatze on quark masses and mixings. It is shown that
starting from arbitrary quark mass matrices and making a suitable weak basis
transformation one can obtain some of these sets of zeros which therefore have
no physical content. We then analyse the physical implications of a
four-texture zero Ansatz which is in agreement with all present experimental
data.Comment: 11 pages, typeset using revte
Spontaneous leptonic CP violation and nonzero
We consider a simple extension of the Standard Model by adding two Higgs
triplets and a complex scalar singlet to its particle content. In this
framework, the CP symmetry is spontaneously broken at high energies by the
complex vacuum expectation value of the scalar singlet. Such a breaking leads
to leptonic CP violation at low energies. The model also exhibits an flavour symmetry which, after being spontaneously broken at a high-energy
scale, yields a tribimaximal pattern in the lepton sector. We consider small
perturbations around the tribimaximal vacuum alignment condition in order to
generate nonzero values of , as required by the latest neutrino
oscillation data. It is shown that the value of recently measured
by the Daya Bay Reactor Neutrino Experiment can be accommodated in our
framework together with large Dirac-type CP violation. We also address the
viability of leptogenesis in our model through the out-of-equilibrium decays of
the Higgs triplets. In particular, the CP asymmetries in the triplet decays
into two leptons are computed and it is shown that the effective leptogenesis
and low-energy CP-violating phases are directly linked.Comment: 17 pages; 6 figures; references added and typos corrected. Final
version to appear in PR
CP violation conditions in N-Higgs-doublet potentials
Conditions for CP violation in the scalar potential sector of general
N-Higgs-doublet models (NHDMs) are analyzed from a group theoretical
perspective. For the simplest two-Higgs-doublet model (2HDM) potential, a
minimum set of conditions for explicit and spontaneous CP violation is
presented. The conditions can be given a clear geometrical interpretation in
terms of quantities in the adjoint representation of the basis transformation
group for the two doublets. Such conditions depend on CP-odd pseudoscalar
invariants. When the potential is CP invariant, the explicit procedure to reach
the real CP-basis and the explicit CP transformation can also be obtained. The
procedure to find the real basis and the conditions for CP violation are then
extended to general NHDM potentials. The analysis becomes more involved and
only a formal procedure to reach the real basis is found. Necessary conditions
for CP invariance can still be formulated in terms of group invariants: the
CP-odd generalized pseudoscalars. The problem can be completely solved for
three Higgs-doublets.Comment: RevTeX4 used. Minor modifications, in particular, the parameter
counting of . v3: Eqs.(28)-(31) correcte
Hierarchy plus anarchy in quark masses and mixings
We introduce a new parameterisation of the effect of unknown corrections from
new physics on quark and lepton mass matrices. This parameterisation is used in
order to study how the hierarchies of quark masses and mixing angles are
modified by random perturbations of the Yukawa matrices. We discuss several
examples of flavour relations predicted by different textures, analysing how
these relations are influenced by the random perturbations. We also comment on
the unlikely possibility that unknown corrections contribute significantly to
the hierarchy of masses and mixings.Comment: LaTeX, 18 pages, 16 PS figure
Large Neutrino Mixing with Universal Strength of Yukawa Couplings
We analyse, within the framework of universal strength for Yukawa couplings
(USY), various structures for the Dirac and Majorana neutrino mass matrices
giving rise, through the see-saw mechanism, to a degenerate mass spectrum. A
specific USY ansatz is presented for the charged lepton and neutrino effective
mass matrix, leading to quasi-degenerate neutrinos and a leptonic mixing matrix
which provides a large angle solution for both the atmospheric and solar
neutrino problems.Comment: 7 pages, ReVTeX, small comments adde
A Complex Case of Cholestasis in a Patient with ABCB4 and ABCB11 Mutations
The low-phospholipid-associated cholelithiasis (LPAC) syndrome is a form of symptomatic cholelithiasis occurring in young adults, characterized by recurrence of symptoms after cholecystectomy and presence of hepatolithiasis. The case refers to a healthy 39-year-old Caucasian male who presented with abdominal pain and jaundice. His blood tests showed conjugated hyperbilirubinemia and elevated liver enzymes (total bilirubin 6.65 mg/dL, Îł-glutamyltransferase 699 IU/L) and abdominal computed tomography revealed dilation of common bile duct and left intrahepatic ducts. Magnetic resonance cholangiopancreatography identified choledocholithiasis, retrieved by endoscopic retrograde cholangiopancreatography, after which there was a worsening of jaundice (total bilirubin 23 mg/dL), which persisted for several weeks, possibly due to ciprofloxacin toxicity. After an extensive workup including liver biopsy, the identification of two foci of hepatolithiasis on reevaluation abdominal ultrasound raised the hypothesis of LPAC syndrome and the patient was started on ursodeoxycholic acid, with remarkable improvement. Genetic testing identified the mutation c.1954A>G (p.Arg652Gly) in ABCB4 gene (homozygous) and c.1331T>C (p.Val444Ala) in ABCB11 gene (heterozygous). In conclusion, we describe the unique case of an adult male with choledocholithiasis, hepatolithiasis, and persistent conjugated hyperbilirubinemia after retrieval of stones, fulfilling the criteria for LPAC syndrome and with possible superimposed drug-induced liver injury, in whom ABCB4 and ABCB11 mutations were found, both of which had not been previously described in association with LPAC.info:eu-repo/semantics/publishedVersio
How is the accounting academy playing the publication game? Type of authorship and international diversity and networks
This study analyses 3,262 papers published in 18 accounting top journals between 2013 and 2017. We have classified these papers based on the type of authorship in Solo (only one author), Homogeneous Multiple (more than one author from the same university), Heterogeneous National (with authors from different universities from the same country) and Heterogeneous International (with authors from universities belonging to different countries). We perform a set of cluster analysis, which suggests a classification of the papers distinguishing between two broad groups of journals: the North American journals, where there is a predominance of national
networks and where most authors are affiliated to a North American journal, and the Non-North American journals, where there is a predominance of international networks and a higher level of authors’ international diversity. Regarding the heterogeneous international authorship, we perform a social network analysis suggesting that researchers affiliated with North-American universities and their counterparts from European universities seem to ignore each other. Whereas the first have been publishing mainly with co-authors affiliated with universities from Asia, the latter have been publishing articles with one another.info:eu-repo/semantics/acceptedVersio
Heat conduction in the hollow sphere with a power-law variation of the external heat transfer coefficient
The conduction phenomenon in an insulated sphere is re-worked through a dimensionless approach, where the heat transfer coefficient dependence on the external radius and on the surface temperature, as in the case of forced and free convection, is taken into account. Assuming a power law variation of the convection coefficient [1, 2], and using the results of Sparrow [3], equations and graphs for the most important dimensionless parameters are presented. The developed equations show, for example, that as the insulation thickness increases the heat transfer rate tends to a positive value, independent of the considered case: constant convection coefficient, forced or free convection.http://www.sciencedirect.com/science/article/B6V3J-42MP1M2-3/1/6228c6d77bbaac53e7833e6cd67d8ef
Heat conduction in the hollow sphere with a power-law variation of the external heat transfer coefficient
The conduction phenomenon in an insulated sphere is re-worked through a dimensionless approach, where the heat transfer coefficient dependence on the external radius and on the surface temperature, as in the case of forced and free convection, is taken into account. Assuming a power law variation of the convection coefficient [1, 2], and using the results of Sparrow [3], equations and graphs for the most important dimensionless parameters are presented. The developed equations show, for example, that as the insulation thickness increases the heat transfer rate tends to a positive value, independent of the considered case: constant convection coefficient, forced or free convection.http://www.sciencedirect.com/science/article/B6V3J-42MP1M2-3/1/6228c6d77bbaac53e7833e6cd67d8ef
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